There are problems when increasing the number of valves used on frac locations. The valves are going to be either zipper or manifold valves etc. In any event these are the surface valves that control where the fluid is flowing on the surface as opposed to the downhole valves. They could be high-pressure gate valves involved in the fracking process or they might be a blowout preventer stack involved in well control.
One of the issues in a frac type application is most if not all of the surface valves, such as those described above, have to be greased fairly frequently, in some instances on an hourly basis. Currently the operator has to move the grease/lubricant connection hoses from valve to valve by hand. Requiring personnel to disconnect each hose from its fining, unscrew it etc. and then connect each hose to something else such as another fitting etc. In many instances the valves are pressurized to much as 20,000 psi such that if a check valve fails there is a safety issue. The safety issue stems from the operating parameter, where in order to inject lubricant into the valve, the pressure in the wellhead manifold must be overcome which means that the pressure of the lubricant in many instances is 15,000 to 20,000 psi to overcome the pressure inside the valve, typically wellhead pressure. The valves are also usually in an elevated situation which means that the person disconnecting the hoses by hand must climb upon a ladder or other means in order to reconnect each hose to another valve. In other instances, the valves may be difficult to reach even when not elevated. The valves may be oil-soaked or dripping causing unsafe footing and other hazards. The valves are typically near the wellhead which means that the operator may be an environment for hydrogen sulfide gas is present or where explosive gases are present.
In order to safely disconnect the hose, the pressure at the fitting must be relieved. Therefore, the pressure in the manifold must be relieved by halting the pumps, isolating the fitting from the wellbore pressure, and bleeding off the pressure that is in the tubular. Typically, the fittings used have a built-in check valve that allows many operators to forgo the step of bleeding off the pressure in the tubular prior to disconnecting and reconnecting the fittings. However, should the check valve fail, the person disconnecting the fitting may be injured due to the high pressure in the line.
With the popularity of multiple stacks growing there may be eight or more wellheads on a common location all of which are being fraced via the same manifold. In such instances the operator may have in excess of 40 valves thereby increasing the chance that the wrong fitting has been disconnected and or the wrong fitting has been reconnected. Additionally, because the valves have to be lubricated frequently the time to disconnect and then reconnect each line and fitting and then lubricate each valve tends to become excessive. In many instances the time required to lubricate the valves exceeds 50% of the time it takes to frac a well. In other words, disconnecting and reconnecting lines and fittings to appropriately lubricate the valves presents a problem where the operator a) has to connect the right unit at the right time, b) shut down the correct portions of plumbing at the right time, c) safety issues to the personnel performing the operations, and d) due to the location issues, noise issues, etc. the operator may have difficulty determining exactly how much lubricant is actually pumped into a particular valve. The result is that in many instances the valves may be under greased or over greased.
An issue in lubricating the frac valves is determining how much lubricant is pumped into a particular valve. Usually the pump and lubricant are over 100 feet away from the wellhead where the valves are located in order to isolate the pumps and lubricants from the potential explosive and hydrogen sulfide issues at the wellhead. Such long distances also significantly increase the time it takes to lubricate each frac valve as the operator has to shut down the correct portion of the valving (or rely on the check valves), walk at least 100 feet to the valve manifold, place the ladder in the correct position, get on the ladder in a hazardous environment in order to disconnect a fitting that is potentially subject to 15,000 psi pressure, reconnect the fitting to the desired valve, get down off the ladder, walk back over to the pump and lubricant that to the pump and lubricant, turn the pump on, then either wait a predetermined period of time, a certain number of pump strokes, or until the pump reaches a certain amount of pressure, turn the pump off, and repeat for the next valve and repeat up to 40 times per hour of operation.
In many instances two people will work together to lubricate the valves with one person at the wellhead disconnecting and reconnecting the fittings while the other person remains with the pump and lubricant to turn the pump on and off. Unfortunately, in many instances with the noise from fluid flowing through the various tubulars and the frac pumps that even with radios it is difficult to communicate one person to another.
The problem with under-lubricating a valve is that you cut down on the life expectancy of that valve. On the other hand, when you over-lubricate a valve expensive lubricant is wasted. Such lubricant may cost several thousand dollars per barrel. Additionally, in many instances the lubricant may interfere with the operation of certain tools in the wellbore such as fishing tools.